Java: Float to hex and reverse

Question

Heyho,

i got a little question. So I got a measurement device and i retrieve the data via modbus. I usually check the values via "Simply Modbus TCP Client" which displays me the correct data. Now I want to automate this process which takes me into trouble.

I get the correct response but the tricky part seems to be the conversion. I get the same response in hex but when I convert it, I won't get the same result.

Take a look at the Screenshot

There you can see the response on the left, the bytes (4175 AF8A) on the right and the corresponding value (22739113). I expect "bytes" to be a hex representation but I can't convert them into a decimal number.

I wrote a small java-program to display these numbers and their conversions.

public static void main(String[] args) {

    HashMap<String, Integer> values = new HashMap<>();
    values.put("4175AF52", 22738214);
    values.put("41D61FAC", 1484698204);
    values.put("419A08A0", 109193237);

    Iterator it = values.entrySet().iterator();
    while (it.hasNext()) {
        System.out.println("/************************************************/");
        Map.Entry pair = (Map.Entry) it.next();
        int hexIntepretation = (int) Long.parseLong((String) pair.getKey(), 16);

        // Print the result
        System.out.println(pair.getKey() + " = " + pair.getValue());
        System.out.println("Expected:\t" + pair.getValue());
        System.out.println("Hex to Int:\t" + hexIntepretation);
        System.out.println("Int to Hex:\t" + Integer.toHexString((int) pair.getValue()));
        System.out.println("Float to Hex:\t" + Float.toHexString((int) pair.getValue()));
        System.out.println("Hex to Int:\t" + Integer.parseInt((String) pair.getKey(), 16));

        it.remove(); // avoids a ConcurrentModificationException
    }
}

Running this snippet gives this output:

/*******************************************/
419A08A0 = 109193237
Expected:       109193237
Hex to Int:     1100613792
Int to Hex:     6822815
Float to Hex:   0x1.a08a06p26
Hex to Int:     1100613792
/*******************************************/
41D61FAC = 1484698204
Expected:       1484698204
Hex to Int:     1104551852
Int to Hex:     587eb25c
Float to Hex:   0x1.61facap30
Hex to Int:     1104551852
/*******************************************/
4175AF52 = 22738214
Expected:       22738214
Hex to Int:     1098231634
Int to Hex:     15af526
Float to Hex:   0x1.5af526p24
Hex to Int:     1098231634

No matter what I do, I can't get the values. BUT when I do "float-to-hex", I will find some of the initial values in there.

Example:

4175AF52 = 22738214

Float to Hex: 0x1.5af526p24

Yet I can't put the pieces together to solve this puzzle. Any help is appreciated!

Answer 1

It says "64 bit float" but the GUI is only showing you 32 bits. Obviously the view cuts the other 4 bytes off but in the field on the left, you can see them.

As you already mentioned, when you copy all the content from the "bytes" column, you'll also get the "missing" ones.